1. Field of the Invention
The present invention relates to a communication system mountable on a car, communication apparatus mountable on a car, and a communication method mountable on a car, which implements high speed data communication between respective apparatuses among a plurality of apparatuses mountable on a car.
2. Description of Related Art
Conventionally, several electronic devices are mounted on a car, which perform several operations. For controlling the performances of these electronic devices, several ECUs (electronic control units) are mounted on the car. Further, for working the several ECUs in cooperation, each ECU is connected to the other ECUs via a network and shares information with data transmission. To achieve these configurations, a CAN (controller area network) is well utilized as a communication protocol (see, non-patent document 1, and non-patent document 2).
Under the protocol of CAN, several ECUs are connected to a bus that is consisted of a twisted-pair cable to transfer an activation signal. Each ECU sends and receives digital data represented by the activation signal. Further, the CAN is a protocol for serial communication. Thus, only one ECU can perform data sending among several ECUs connected to a bus for CAN. Until the ECU completes the data sending, the other ECUs are controlled to wait. When some ECUs simultaneously perform data sending, arbitrating is performed on the basis of IDs applied to data and the highest priority data is controlled to be sent.    [non-patent document 1] ISO 11898-1: 2003 Road vehicles—Controller area network (CAN)—Part 1: Data link layer and physical signaling    [non-patent document 2] ISO 11519-1: 1994 Road vehicles—Low-speed serial data communication—Part 1: General and definitions